I heartily agree with their fountain pen choices. The Pilot Metropolitan is insanely good for a cheap pen that you can take anywhere and the TWSBI GO is my go-to daily driver. It leads me to believe that the rest of the reviews are likely good.
Is this just a fact of life with fountain pens in general? I love the writing but keeping them clean & operational has been non-trivial for me.
The pressure changes when flying can force ink out the nib as well. I've heard people say you can prevent it by having the reservoir completely full but I fly with it empty or usually just leave it at home.
That said, I don't travel with them, practically speaking.
Otherwise, ink shouldn't come out unless there is a flaw in the pen (which many ultra cheap pens have).
I've not tried the Moonman, but Jinhao/PenBBS are solid for me. Rarely do they "leak".
I have pens from all of these companies and they are some of my favorite brands.